closures

问题 let sortedNumbers = numbers.sort { $0 > $1 } print(sortedNumbers) Can anyone explain, what $0 and $1 means in swift? More Sample array.forEach { actions.append($0) } 回答1: $0 is the first parameter passed into the closure. $1 is the second parameter, etc. That closure you showed is shorthand for: let sortedNumbers = numbers.sort { (firstObject, secondObject) in return firstObject > secondObject } 回答2: It represents shorthanded arguments sent into a closure, this example breaks it down: Swift 4

问题 I wrote this fast-templating function: var templatize = function(string) { return function (string) { return string.replace(/{{(.*?)}}/g, function(pattern, match) { value = this[match]; if (value) { return value; } else { return pattern; } }); }.call(this, string); } Which does this: var foo = "bar", bar = "foo"; templatize("We are {{foo}} and {{bar}}, but not {{crazy}}"); // "We are bar and foo but not {{crazy}}" I'm quite happy with this except that I have scoping problem. For sure, the

问题 I can run this code fn testf(host: &str) {} fn start(host: &str) { testf(host); testf(host); } but for some reason, I can't run this one: fn testf(host: &str) {} fn start(host: &str) { thread::spawn(move || testf(host)); thread::spawn(move || testf(host)); } because of the following error src/server.rs:30:5: 30:18 error: the type `[closure@src/server.rs:30:19: 30:38 host:&str]` does not fulfill the required lifetime src/server.rs:30 thread::spawn(move || testf(host)); ^~~~~~~~~~~~~ note: type

问题 I'm trying to find out more about closures in Javascript and was going through this: https://developer.mozilla.org/en/JavaScript/Guide/Closures#Practical_closures According to this article, by using such a function: function makeSizer(size) { return function() { document.body.style.fontSize = size + 'px'; }; } var size12 = makeSizer(12); var size14 = makeSizer(14); var size16 = makeSizer(16); We can then make use of such statements to increase/decrease the font-size of text on a page:

问题 Let's say I have these two functions: function fnChanger(fn) { fn = function() { sys.print('Changed!'); } } function foo() { sys.print('Unchanged'); } Now, if I call foo() , I see Unchanged , as expected. However, if I call fnChanger first, I still see Unchanged : fnChanger(foo); foo(); //Unchanged Now, I assume this is because foo is not being passed to fnChanger by reference, but I may be wrong. Why does fnChanger not change foo to print Changed! ? Furthermore, how can I get fnChanger to

问题 We do some dynamic creation of parallel steps in some of our jobs. Thanks to this thread I found how to dynamically create the map with parameters for use in the parallel step. However now I wanted to reuse parts of the code which is used to create those parallel steps. For this I feel that I would need to curry the closures. However currying seems not to work correctly. Referencing the loop variable (valueCopy) inside the closure does the right thing (as mentioned here) but currying does not

问题 Javascript's array iteration functions ( forEach , every , some etc.) allow you to pass three arguments: the current item, the current index and the array being operated on. My question is: what benefits are there to operating on the array as an argument, vs. accessing it via the closure? Why should I use this: myArray.forEach(function(item, i, arr) {doSomething(arr);}); Instead of this: myArray.forEach(function(item, i) {doSomething(myArray);}); 回答1: It is possible that you want to pass a

问题 When I run the code below the output is "DelegateDisplayIt", typically repeated 1-4 times. I've run this code probably 100 times, and not once has the output ever been "ParameterizedDisplayIt". So it seems the manner in which the thread is created and subsequently started affects how the parameter is passed. When creating a new thread with an anonymous delegate the parameter is a reference back to the original variable, but when created with a ParameterizedThreadStart delegate the parameter

问题 I'm running in a loop and kicking off tasks in the following manner: var iResult = new List<Task>(); foreach(var i in myCollection) { var task = Task.Factory.StartNew(() => DoSomething(), TaskCreationOptions.LongRunning); task.ContinueWith(m => myResponseHandler(m.Result)); iResult.Add(task); } Within my DoSomething() method, I have a timer: public static myMsg DoSomething() { var timer = System.Diagnostics.Stopwatch.StartNew(); DoLongRunningTask(); //If it matters this hits a REST endpoint

问题 I have something like this: use std::sync::Arc; fn main() { let arc = Arc::new(42); move || { arc.clone() }; move || { arc.clone() }; } I am getting: error[E0382]: capture of moved value: `arc` --> src/main.rs:6:19 | 5 | move || { arc.clone() }; | ------- value moved (into closure) here 6 | move || { arc.clone() }; | ^^^ value captured here after move | = note: move occurs because `arc` has type `std::sync::Arc<i32>`, which does not implement the `Copy` trait I understand why I am getting